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A mathematician's way of converting miles to kilometers

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Re: A mathematician's way of converting miles to kilometers

#71

Post by raverbashing »

jedberg wrote: post #46
ghaff wrote: post #14

Earlier quoted context omitted.

There are a fair number of people who seem to take personal offense that the US (and to some degree the UK) don't use SI for everyday types of things and add it to their laundry list of grievances about the US generally. Never mind the fact that SI is generally used for engineering and other areas where it has legitimate advantages (which miles vs. kilometers doesn't really in day-to-day life).

> which miles vs. kilometers doesn't really in day-to-day life Standard units are much more useful in carpentry. It's a lot easier when you can divide by 2,3,4, and 6.

Oh yes, then you need to figure out if 7/16 is bigger or smaller than 3/4. No, thanks.

You can easily divide by 2 and 4 in metric, because guess what, you just add a decimal point to your measure and 10cm/4 is 2.5cm and not some crazy fraction or weird unit and the math is not harder if you're dealing with 10m as opposed to 10cm.

10cm/3 is 3.3cm or whatever the precision of your tools is. It's the same "problem" (it isn't) with dividing 1ft in 5 for example. You go by the tolerance of your tools

Re: A mathematician's way of converting miles to kilometers

#72

Post by mkl »

dfeojm-zlib wrote: post #52

What's interesting is that the absolute error converges to ~0.5399705049968784% (or a floating-point type or constant imprecision were introduced).

.5*(1+sqrt(5))/1.609344 - 1 = 0.00539970867005111... actually, but that doesn't seem interesting either. What do you mean?

Re: A mathematician's way of converting miles to kilometers

#74

Post by rocqua »

ghaff wrote: post #70
sergioj97 wrote: post #66

Earlier quoted context omitted.

I agree it's not worth the hate, but in my opinion SI units are much more convenient. Using your own example, miles vs kilometers may not feel like a big difference, but the fact that you have proportional units (mm, cm, m, km) for any possible distance has the potential to save you a lot of trouble. Having completely different units for the same thing (land miles / nautical miles for distance), usually not proportio…

That's fair enough. Whatever the advantages of Imperial in some narrow contexts, I'm not sure very many would argue for them absent legacy. On the other hand, it's pretty much an academic debate because a switch isn't happening for mainstream use. The desire and political will just aren't there. The little push that once existed is essentially gone whatever some tech types might want.

I like arguing for arcane standards, and there are aspects of the imperial system I like.

Specifically, I tend to advocate for a base 12 system based arround the inch. Base 12 because the very structured multiplication table, which also makes for easy dividing. The inch because I find my lengtg estimation accuracy to be better captured by inches.

Re: A mathematician's way of converting miles to kilometers

#77

Post by aerophilic »

Since we are talking about “useful approximations”, one I have always found useful in robotics is doubling m/s to get miles per hour. While a bit “rough” usually “good enough” for when thinking about normal driving speeds. Here are some examples:

    1 m/s ~ 2 mph (2.2 mph)
    5 m/s ~ 10 mph (11.2 mph)
    10 m/s ~ 20 mph (22.4 mph)
    20 m/s ~ 40 mph (44.7 mph)
    30 m/s ~ 60 mph (67.1 mph)
You could argue that it is a very rough estimation, but I find that most times you are just trying to get a “rough speed” when doing this conversion anyway.

Re: A mathematician's way of converting miles to kilometers

#79

Post by fhars »

sergioj97 wrote: post #66
ghaff wrote: post #14

Earlier quoted context omitted.

There are a fair number of people who seem to take personal offense that the US (and to some degree the UK) don't use SI for everyday types of things and add it to their laundry list of grievances about the US generally. Never mind the fact that SI is generally used for engineering and other areas where it has legitimate advantages (which miles vs. kilometers doesn't really in day-to-day life).

I agree it's not worth the hate, but in my opinion SI units are much more convenient. Using your own example, miles vs kilometers may not feel like a big difference, but the fact that you have proportional units (mm, cm, m, km) for any possible distance has the potential to save you a lot of trouble. Having completely different units for the same thing (land miles / nautical miles for distance), usually not proportio…

My favourite use of units is still the „2mm Scale Association“, a British model railroad club that builds their trains at a scale or two millimeteres to the foot (which is slightly larger than the standard N-track). It always blows my mind when I try to think how people come up with a scale like that.

Re: A mathematician's way of converting miles to kilometers

#80

Post by jupblb »

eps wrote: post #4

In related news - pounds to kilos is "divide by 2, less 10%". Very precise too. 160lbs = 80 - 8 = 72kg

So n * (1-0.5) * (1-0.1)... This could also work for miles to km conversion in a similar way: n * (1+0.5) * (1+0.1). Not as accurate as golden ratio but still acceptable. :D
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